Leaching of Cu, Zn, and Pb from sulfidic tailings under the use of sulfuric acid and chloride solutions

The imbalance between raw materials of high economic importance and their supply has increased the search for new approaches to obtain valuable elements from mining tailings. In this study, the extraction of copper, zinc, and lead from sulfidic tailing in sulfate–chloride media was investigated. A 3 3 Box–Behnken design was applied to evaluate three variables over a 4-h testing period: sulfuric acid concentration (0.01–1.0 mol/L H 2 SO 4 ), sodium chloride (10–60 g/L NaCl), and temperature (20–70 °C). The design showed two optimum working regions: a combination of a high NaCl level, low H2SO4 level, and medium temperature level for lead leaching, while for copper and zinc, a combination of a medium–high H 2 SO 4 level and a high temperature level. The concentration of NaCl had only a slight impact on their leaching. Based on these results, two-stage leaching was performed. The first stage was carried out under an experimental condition that favored the leaching of lead (60 g/L NaCl, 0.01 mol/L H 2 SO 4 , 45 °C, 1 h, 10:1 liquid-to-solid ratio), whereas the second stage maximized the leaching of copper and zinc (60 g/L NaCl, 0.5 mol/L H2SO4, 70 °C, 24 h, 10:1 liquid-to-solid ratio). The global leaching rate was 66.8 ± 3.0% copper, 84.1 ± 5.2% zinc, and 93.9 ± 3.2% lead. The iron and arsenic content were also leached by about 20 and 50% at the end of the second stage. The study demonstrated that the use of sulfate–chloride media in a two-stage leaching considerably improved the extraction of the desired metals and was, therefore, suitable for their recovery

Drilling tool geometry evaluation for reinforced composite laminates

In this work, a comparative study on different drill point geometries and feed rate for composite laminates drilling is presented. For this goal, thrust force monitoring during drilling, hole wall roughness measurement and delamination extension assessment after drilling is accomplished. Delamination is evaluated using enhanced radiography combined with a dedicated computational platform that integrates algorithms of image processing and analysis. An experimental procedure was planned and consequences were evaluated. Results show that a cautious combination of the factors involved, like drill tip geometry or feed rate, can promote the reduction of delamination damage

An SFC-enabled approach for processing SSL/TLS encrypted traffic in future enterprise networks

In this paper, we propose an architecture based on NFV and SDN which allows to balance traffic analysis techniques using a Classifier. It steers flows to the appropriate Service Function Chaining (to open traffic or not) according to network requirements (such as, effectiveness, flexibility, scalability, performance, and privacy). The SSL/TLS traffic processing is carried-out by the centerpiece of this work, the SFC-enabled MITM. A Proof-of-Concept was conducted (focusing on our SFC-enabled MITM) which showed that functionalities lost due to encryption (Content Optimization, Caching, Network Anti-virus, and Content Filter) were recovered when processing opened traffic within its Service Function Chains. We also evaluated its impact on performance. The results show that cipher suite overhead plays a role but can be mitigated, the Classifier can alleviate the performance overhead of different traffic analysis techniques, network functions have lower impact to performance, and Service Function Chaining length influences page load time.publishe

Orchestrating an SFC-enabled SSL/TLS traffic processing architecture using MANO

The heterogeneity of 5G requirements commands more complex network architectures, imposing the need for network orchestration. ETSI NFV MANO is the standard which defines a common framework for vendors and operators to integrate their orchestration efforts. In this paper, we evaluated how an ETSI NFV MANO compliant orchestrator (OSM) fares while orchestrating an SFC-enabled SSL/TLS encrypted traffic processing architecture, which supports both edge and cloud deployments. A quantitative evaluation was carried-out, which assessed the responsiveness and overheads of OSM, as well as the actual functionality of our SSL/TLS processing architecture (with edge computing components). A qualitative evaluation was also carried-out, providing insight into the maturity of the current OSM release, what works well, what requires workarounds, and the actual limitations. A demonstration of the architecture evaluated in this work was accepted as a contribution to the ETSI OSM PoC Framework.publishe

Drilling delamination study on carbon reinforced laminates - tool and feed rate effects

The characteristics of carbon fibre reinforced plastics had widespread their use. In order to join different components, drilling is often necessary. It is known that a drilling process that reduces the drill thrust force can decrease the risk of delamination. In this work, three combinations of the drilling process are compared: tool diameter and geometry and feed rate. The parameters considered for analysis include: thrust force, delamination extension and mechanical strength. This work shows that a proper combination of the drilling variables can contribute to reduce the delamination damage

Rarity of monodominance in hyperdiverse Amazonian forests.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors

Estudo da delaminação associada à furação de compósitos reforçados com fibras de vidro e de sisal

O crescente conhecimento das suas propriedades e o avanço nas técnicas do seu processamento têm permitido uma utilização cada vez mais variada dos materiais compósitos de matriz polimérica. Embora as aplicações mais frequentes estejam relacionadas com o uso de fibras de vidro ou de carbono como material de reforço, a utilização de fibras de reforço naturais tem vindo a merecer maior atenção. A utilização deste tipo de compósitos está limitada pela desconfiança que resulta da inconsistência das suas propriedades mecânicas e susceptibilidade a operações de maquinagem.Neste trabalho são comparadas placas laminadas com dois tipos de reforços: fibra de vidro e fibra de sisal, ambos obtidos por processamento manual. Para caracterização das principais propriedades de resistência, como a tensão de rotura ou o módulo de elasticidade, foram realizados ensaios mecânicos. De seguida, as placas foram furadas com dois tipos de broca helicoidal e Brad e duas velocidades de avanço baixa e alta sendo a velocidade de corte constante. Após furação, as placas foram radiografadas com recurso a radiografia digital com contraste e as imagens obtidas foram sujeitas a técnicas de processamento e análise de imagem através da utilização de uma plataforma computacional que integra uma rede neuronal para segmentar as imagens. Desta forma foi possível obter resultados da extensão de dano associado à operação de furação delaminação que seguidamente foram correlacionados com os resultados dos ensaios mecânicos complementares.As conclusões deste trabalho permitem contribuir para uma melhor compreensão das possíveis utilizações dos compósitos de fibra natural relativamente a compósitos mais tradicionais

Mutation Size Optimizes Speciation in an Evolutionary Model

The role of mutation rate in optimizing key features of evolutionary dynamics has recently been investigated in various computational models. Here, we address the related question of how maximum mutation size affects the formation of species in a simple computational evolutionary model. We find that the number of species is maximized for intermediate values of a mutation size parameter μ; the result is observed for evolving organisms on a randomly changing landscape as well as in a version of the model where negative feedback exists between the local population size and the fitness provided by the landscape. The same result is observed for various distributions of mutation values within the limits set by μ. When organisms with various values of μ compete against each other, those with intermediate μ values are found to survive. The surviving values of μ from these competition simulations, however, do not necessarily coincide with the values that maximize the number of species. These results suggest that various complex factors are involved in determining optimal mutation parameters for any population, and may also suggest approaches for building a computational bridge between the (micro) dynamics of mutations at the level of individual organisms and (macro) evolutionary dynamics at the species level